Oil-heated once-through heater with apparatus for pre-heating the mixing chamber

ABSTRACT

An oil gasification burner comprises a mixing chamber into which oil is sprayed to be vaporized by the chamber heat to produce a combustible gas. This gas, along with air moves downstream from the chamber through a plate and is burned on the downstream side of the plate to heat the heat exchanger of a once-through water heater. A blower communicates with the chamber through a conduit for introducing air for combustion into the chamber. An auxiliary oil burner in the conduit is operated during start-up to supply heat for heating the chamber so that it will be prepared to gasify the oil subsequently sprayed into the chamber.

United States Patent [191 Reichmann OIL-HEATED ONCE-THROUGH HEATER WITH APPARATUS FOR PRE-HEATYNG THE MIXING CHAMEER Inventor: Horst Reichmann, Wuppertal-Elberfeld, Germany Assignee: Joh Vaillant KG. Remscheid, Germany Filed: .llune 16, 197

Appl. No.: 153,587

[30] Foreign Application Priority Data July 6, 1970 Austria A 6062/70 References Cited UNITED STATES PATENTS 12/1968 Reichmann 122/367 June 12, 1973 1,355,443 10/1920 Auger 431/239 FOREIGN PATENTS OR APPLICATIONS 1,161,256 8/1969 Great Britain 126/350 R Primary ExaminerWilliam F. ODea Assistant ExaminerWilliam C. Anderson Attorney-Howard H. Darbo, Louis Robertson, and Edward C. Vandenburgh [57] ABSTRACT An oil gasification burner comprises a mixing chamber into which oil is sprayed to be vaporized by the chamber heat to produce a combustible gas. This gas, along with air moves downstream from the chamber through a plate and is burned on the downstream side of the plate to heat the heat exchanger of a once-through water heater. A blower communicates with the chamber through a conduit for introducing air for combustion into the chamber. An auxiliary oil burner in the conduit is operated during start-up to supply heat for heating the chamber so that it will be prepared to gasify the oil subsequently sprayed into the chamber.

3 Claims, 1 Drawing Figure OIL-HEATED ONCE-THROUGH HEATER WITH APPARATUS FOR PRE-HEATING THE MIXING CHAMBER BACKGROUND AND SUMMARY OF THE INVENTION The invention relates to a once-through water heater (forced circulation heater) with heat exchanger in the form of a plate block, traversed by once-through pipes and functioning as the termination of a heating shaft and having an oil gasification burner with blower disposed in the lower part of the heating shaft.

The prior art includes an oil gasiflcation burner for use in conjunction with such once-through heaters and in which a combustible mixture of air and gasified oil is formed in a conically flared mixing chamber. The mixing chamber terminates in a burner plate having small burner apertures. The combustible mixture flows through these apertures from the mixing chamber and burns with a blue flame at the opposite side of the plate.

To heat the mixing chamber and the air introduced therein sufficiently to gasify the oil introduced into the chamber upon start-up, electric heating coils have been proposed. This prevents the formation of condensate when the main oil burner is started.

It will be apparent that it is difficult and therefore expensive to provide electric heating coils for heating the combustion air and for heating the mixing chamber in which the oil is gasified. Moreover, maintenance is difficult owing to the concealed position of the said heating coils.

It is therefore necessary to simplify the problem of heating the mixing chamber including the burner plate upon cold starting, to provide better accessibility and to reduce the cost of production.

According to the invention, the problem is solved in that an auxiliary burner, including an oil injection nozzle and an associated ignition electrode, is disposed concentrically in the blower duct. Therefore, the blower air, before entering into the mixing chamber, is heated during the cold start period. The auxiliary burner is started when the air blower is started so that hot air flows through the mixing chamber and the main burner to heat the same. The oil supply to the main burner nozzle is initiated and the oil-gas air mixture is ignited only after the mixing chamber is sufficiently heated. Thereafter, the auxiliary burner is shut down. Further, the preheated combustion air flows through the annular concentric ducts surrounding the heating shaft and principally on the wall of the mixing chamber where the air is provided with a temperature which is so high that the oil droplets of the oil mist injected by the high-pressure nozzle become gasified to produce a combustible oil-gas air mixture.

DESCRIPTION OF THE DRAWING The drawing is a section, in schematic form, of an embodiment of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENT A heating shaft 1, constructed of steel sheet, defines a heating chamber 2. At the top, the heating shaft 1 is closed by a heat exchanger in the form of plate block 3. The end of the heating chamber is formed by an exhaust gas collecting hood 4 which terminates in an exhaust gas pipe connection through which the exhaust gas is conducted in a known manner to the chimney.

The plate block 3 is traversed by once-through water conduits which are connected to a cold water inlet pipe 5 and a hot water feed pipe 6.

The main burner includes a burner plate 7, provided with burner apertures 7. Plate 7 is positioned intermediate theends of the shaft 1 and forms a termination for the mixing chamber 8 part of the shaft. The lower part of the mixing chamber 8 is cylindrical and its upper part flares conically and forms a tight seal with the heating shaft 1. The heating shaft 1 and the mixing chamber 8 are surrounded by an annular chamber 9 defined by the sheet steel walls 1 and 9a. The sheet steel wall 9a is supported by a thermally insulating, cupshaped member 10. Wall 11 (open at the bottom) of the mixing chamber 8 extends into member 10. A highpressure nozzle 12 injects oil mist at an acute angle (indicated by dash-dot lines) into the open end of wall 11 of the mixing chamber. An oil delivery line 13 connects the high-pressure nozzle 12 to an oil pump 14. Oil pump 14 is driven by an electric motor 15 which also drives the blower 21. An electrically actuated valve 16 controls the flow through oil line 13. Upstream of the valve 16, a branch line 17 extends from the main line 13 to a high-pressure nozzle 18 of an auxiliary burner. Nozzle 18 is positioned centrally in the air conduit 19 downstream from blower 21. The nozzle of the auxiliary burner has oil flow rate smaller than that of the nozzle 12 and quite insufficient to use up all the oxygen in the air from the blower. Flow through the branch oil line 17 is controlled by the electric valve 20.

The fresh air blower 21 supplies fresh air through the conduit 19 into an annular chamber 22 surrounding the annular chamber 9. Chamber 22 is enclosed by an external wall 22a. The chambers form conduits communicating with mixing chamber 8. While reversing its direction of flow, the fresh air flows from the annular chamber 22 into the annular chamber 9, and after its direction is once again reversed, enters into the mixing chamber 8 from below.

The auxiliary burner 18 is ignited by the ignition electrode 23 while the main burner is ignited by the ignition electrode 24. Monitoring of the main burner is provided by the electrode 25. A thermostat 26 for monitoring the pre-heating of the mixing chamber is disposed in the inlet aperture of the mixing chamber 8.

For cold starting of the burner, the motor 15 is started. Thereupon, the blower 21 delivers air and the oil pump 14 delivers oil. The thermostat 26 (being cold) opens valve 20 to admit oil to the pre-heater burner 18, but closes valve 16. The mixture of oil and air is ignited by the ignition electrode 23 at the auxiliary burner. There is substantially more than a stoichiometric amount of oxygen present in the air passing the auxiliary burner. The hot gases from the auxiliary burner flow successively through the annular ducts 22 and 9 and through the mixing chamber 8. When the mixing chamber is sufficiently heated, the thermostat 26 opens the valve 16 to the burner nozzle 12 and shuts down the auxiliary burner 18 by closing valve 20. The oil mist discharged from the nozzle 12 intcrmixes with the hot air, thus causing the oil droplets to gasify to produce a combustible oil-gas air mixture. This mixture passes through the apertures 7 of the burner plate 7 and burns at the top of the plate with a blue, nonincandescent flame after being ignited by the ignition electrode 24. The apertures are sufficiently small so that the flame stays above the plate.

I claim:

1. In a water heater of the once-through type having a heating shaft, a plate block heat exchanger adjacent one end of the shaft, a first annular chamber surrounding the shaft and having upper and lower ends, said lower end communicating with the other end of the shaft, an oil gasification burner including a burner plate intermediate the ends of the shaft, a second annular chamber surrounding the first annular chamber and having upper and lower ends, said upper ends of the two chambers being in communication, a tubular conduit having one end in communication with the lower end of the second chamber and having a second end, a blower communicating with the second end of the conduit for supplying combustion air having oxygen therein to the shaft, an oil supply nozzle means adjacent the other end of the shaft for supplying oil to the shaft to be vaporized therein and burned at the side of the plate adjacent said one end, and heating means for preliminarily heating said shaft upon the start-up of the burner, the improvement wherein said heating means comprises:

an auxiliary oil injection nozzle in said conduit downstream from said blower to spray oil into said conduit, and an ignition electrode associated with said conduit nozzle for igniting said sprayed oil to produce a flame for heating the air flowing through said conduit to the shaft, said nozzle being of a capacity such that when the oil therefrom is burned the amount of combustion is quite insufficient to use up all of the oxygen supplied by said blower.

2. In a water heater as set forth in claim 1, wherein the oil gasification burner has an oil pump and an oil line from the pump to the nozzle means, and including a branch from said oil line to said conduit nozzle, and a valve in said branch for controlling the flow of oil to the conduit nozzle.

3. In a heater as set forth in claim 2 including a main valve in said oil line between the branch and the oil gasification burner, thermostat means for measuring the temperature in said shaft upstream from said burner plate and connected to said valves for opening said main valve and closing said branch valve when the temperature sensed thereby reaches a predetermined minimum. 

1. In a water heater of the once-through type having a heating shaft, a plate block heat exchanger adjacent one end of the shaft, a first annular chamber surrounding the shaft and having upper and lower ends, said lower end communicating with the other end of the shaft, an oil gasification burner including a burner plate intermediate the ends of the shaft, a second annular chamber surrounding the first annular chamber and having upper and lower ends, said upper ends of the two chambers being in communication, a tubular conduit having one end in communication with the lower end of the second chamber and having a second end, a blower communicating with the second end of the conduit for supplying combustion air having oxygen therein to the shaft, an oil supply nozzle means adjacent the other end of the shaft for supplying oil to the shaft to be vaporized therein and burned at the side of the plate adjacent said one end, and heating means for preliminarily heating said shaft upon the start-up of the burner, the improvement wherein said heating means comprises: an auxiliary oil injection nozzle in said conduit downstream from said blower to spray oil into said conduit, and an ignition electrode associated with said conduit nozzle for igniting said sprayed oil to produce a flame for heating the air flowing through said conduit to the shaft, said nozzle being of a capacity such that when the oil therefrom is burned the amount of combustion is quite insufficient to use up all of the oxygen supplied by said blower.
 2. In a water heater as set forth in claim 1, wherein the oil gasification burner has an oil pump and an oil line from the pump to the nozzle means, and including a branch from said oil line to said conduit nozzle, and a valve in said branch for controlling the flow of oil to the conduit nozzle.
 3. In a heater as set forth in claim 2 including a main valve in said oil line between the branch and the oil gasification burner, thermostat means for measuring the temperature in said shaft upstream from said burner plate and connected to said valves for opening said main valve and closing said branch valve when the temperature sensed thereby reaches a predetermined minimum. 